1. Field of the Invention
This invention relates generally to full duplex two wire voice communication systems and more particularly to a portable device for testing live or dead two wire circuits using a conventional three terminal carbon telephone headset for voice testing and a highly sensitive tuned amplifier for tone testing.
2. Description of the Prior Art
Full duplex two wire voice communication is well known and is generally exemplified in the two wire telephone systems used through the world. Many problems with telephone systems have been addressed, particularly problems associated with compensation for poor transmission. For example, U.S. Pat. No. 3,963,876 issued to R. E. Holts and R. A. Radosevich, discloses a device for providing extra transmit and receive amplification for a conventional telephone set. The device also includes voice switched means to provide sidetone control. This device, like most apparatus associated with improving or testing telephone communications obtains power from the transmit part of a conventional telephone hybrid speech network. In contrast, the test set of the invention is powered from a self contained power supply.
Known telephone test equipment also depends on power available from conventional hybrid speech networks. Thus, communication between repairmen at different field locations or between a repairman and a central office depends upon the existence of a live telephone pair common to the two locations seeking to communicate. This is usually accomplished by a repairman dialing into a central exchange and being connected to another repairman over live wire pairs through the exchange. Such a system typically requires some form of auxiliary wireless communication system to effectively co-ordinate the repair effort. The device of the invention eliminates the problem of the necessity for a live wire pair by including a power supply and conventional hybrid speech circuit in the same unit. This feature not only provides an ability to test dead wire pairs but also obviates the need for an auxiliary communication system.